Percussive drilling machine

ABSTRACT

A machine in which of an air-operated striking rearhead has a body accommodating a hammer piston reciprocating under the action of compressed air so as to deliver blows at a drill steel located at the front end of the machine, and a reversible rotary impulse fronthead has a body accommodating two rotatable and axially movable annular pistons provided with impact projections and indentations formed between the projections, with the pistons being coupled by an interengagement of the respective projections and indentations thereof, the projections and walls of the fronthead body forming work and idle stroke air chambers which are periodically placed in communication via passages with a source of compressed air and the atmosphere, and the projections of one of the annular pistons performing, under the action of air pressure, high-frequency reciprocatory angular oscillations so as to deliver blows with their impact projections at the respective projections of the other annular piston. The rotary impulse fronthead has a ratchet mechanism which ensures the rotation of one of the annular pistons and the drill steel only in one direction. In addition, the rotary fronthead is provided with means adapted to switch over the ratchet mechanism from one rotational direction to the other (from lefthand rotation to righthand rotation, and vice versa) so as to enable right- and lefthand rotation of the drill steel.

United States Paten [191 Bazhal et a1.

[ PERCUSSIVE DRILLING MACHINE [76] Inventors: Anatoly IgnatievichBazhal, ultisa Franko, 30, kv. 42; Alexandr llich Mishkin, ulitsa Gagarina 8, kv. l8; Anatoly Antonovich Bessarab, ulitsa Shevchenko 8, kv:24, all of Zheltye Vody Dnepropetrovskoi oblasti, USSR.

22] Filed: Jan. 15, 1973 21 Appl. N0.;323,40s

[52] US. Cl 173/93, 91/120, 173/108, 418/33 [51] Int. Cl B25d 15/00 [58]Field of Search l73/9393.7, .173/105-109, 9497;-4l8/33 [56] ReferencesCited UN1TED STATES PATENTS 2,457,969 l/l949 Anderson 173/107 1,160,64811/1915 Peck 173/108 3,552,363 1/1971 Funakoshi 418/33 PrimaryExaminer-Henry C. Sutherland Assistant Examiner-William F. Pate, lllAttorney, Agent, or Firm--Holman & Stern [57] I ABSTRACT A seasidenearer; of an snapsrma striking rear- May 21, 1974 head has a bodyaccommodating a hammer piston reciprocating under the action ofcompressed air so as to deliver blows at a drill steel located at thefront end of the machine, and a reversible rotary impulse front:

head has a body accommodating two rotatable and axially movable annularpistons provided with impact projections and indentations formedbetweenT'Ie projections, with the pistons being coupled by aninterengagement of the respective projections and indentations thereof,the projections and Walls of the fronthead body forming work and idlestroke air chambers which are periodically placed in communication viapassages with a source of compressed air and the atmosphere, and theprojections of one of the annular pistons performing, under the actionof air pressure, high-frequency reciprocatory angular oscillations so asto deliver blows with their impact projections at the respectiveprojections of the other annular piston. The rotary impulse frontheadhas a ratchet mechanism which ensures the rotation of one of the annularpistons and the drill steel only in one direction. In addition, therotary fronthead is provided with means adapted to switch over theratchet mechanism from one rotational direction to Y the other (fromlefthand rotation to righthand rotation, and vice versa) so as to enableright and lefthand rotation of the drill steel.

5 Claims, 15 Drawing Figures PATENTEDHAYZI m4 v 3,811,515

sum 3 or s w a, 4am.

s h I minimum 21 I974 8 l 1. 515

saw u or 6 v PERCUSSIVE DRILLING MACHINE BACKGROUND OF THE INVENTION apercussive drilling machine with independent nonl reversible rotation ofa drill steel comprising an airoperated striking rearhead consisting ofa body with a cylindrical bore which accommodates an airdistributionmeans and a hammer piston reciprocating under the action of compressedair so as to deliver, at the end of the work stroke, a blow to a drillsteel located in the front part of the drilling machine, and a rotaryimpulse fronthead located in the front part of the drilling machine arrdcomprising a body with a cylindrical bore which accommodates, located inthe rear part thereof,

an annular striking piston having annular projections, a rotary anvilhaving cooperative projections and indentations so arranged that theirside surfaces and walls of said fronthead body define, during each workand idle stroke, air chambers periodically placed in communication viapassages with a source of compressed air or atmosphere, with theprojections of the annular striking piston performing under air.pressure high-frequency reciprocatory angularj oscillations so as todeliver, at the end of the work stroke, a blow with hammer projectionsat the re-' spective projections ofv the rotary anvil, thereby rotatingthe rotary anvil connected to the drill steel; v ia intermediate parts,and a ratchet mechanism arranged in the front part of the fronthead bodyand comprising a ratchet wheel integral with the fronthead body andpawls mounted on the end face of the rotary anvil facing the drillsteel. In the prior art drilling machine, the ratchet pawls are mountedin such a manner as to enable the rotation of the rotary anvil only inone direction, thereby preventing the rotation of the anvil, which isconnected to the drill steel, in the opposite direction under the actionof the elastic rebound reactive force of the drilling string beingtwisted due to the engagement with the rock. I

The prior art drilling machine permits the rotation,-' of the spindlewith the drill steel only in one direction; which does not allow it'tobe used in drilling deep? holes since it cannot provide formechanization of f the process of disassembling the drilling string.

Furthermore, in the prior art drilling machine the degree of accuracy infitting frictional end faces of the annular pistons as well as the sizeof gaps therebetween,

are determined by their initial mechanical adjustment only. However,since during the operation of the drilling machine under miningconditions, these surfaces are subject tointensive wear, and thisresults in the expansion of axial gaps, changes in theoperational.

parameters of the impulse rotary fronthead and in an excessive airconsumption.

O BIE C TS AND SUMMARY OF THE INVENTION object of the inventionibiibvide a percussive steel, but also offers an opportunity ofreversing the rotation of the drill steel.

Another object of the invention is to provide a percussive drilling"rarest as having a morfia'abie 5 structure.

Still another object of the invention is to provide a percussivedrilling machine which has minimum axial gaps between the end faces ofthe annular pistons,

with the predetermined size of the gaps being automatically maintainedconstant.

These and other'objects of the invention are accomplished by theprovision of a percussive drilling machine with independent rotation ofa drill steel comprising an air-operated striking rearhead define by ofa body with a cylindrical bore which accommodates an air-distributionarrangement and a hammer piston reciprocating under the actiongfcompressed air so as to deliver, at the end of the work stroke, a blowto the drill steel disposed in the front part of the drilling machine,and a rotary impulse fronthead located at the front end of the drillingmachine and comprising a body with a cylindrical bore which accommodatesrotatably mounted annular pistons having imp ac tprojections andindentations formedbetween the projectionswith the annular pistons beingcoupled by an interengagement of the respective projections andindentations thereof so that the side surfaces of the projections andwalls of the fronthead body define, during each work and idle stroke,air chambers which are periodically communication with a source ofcompressed air or atmosphere via passages, and the projections of oneannular "piston performing under the action of air pressure,high-frequencyreciprocatory angular oscillations to deliver blows withthe impact projections at the respective projections of the otherannular piston at the end of the work stroke so as to rotate the drillsteel via intermediate parts, and a ratchet mechanism arranged atthefront end of said fronthead body and comprising a ratchet wheelintegral with the housing of the ratchet mechanism, said housingaccommodating asleeve' provided with movable spring loaded pawls mountedtherein, said pwals engaging the teeth of the ratchet wheel (housing),with the ratchet mechanism ensuring the rotation of one of the annularpistons and the drill steel in only one I direction. In accordance withthe invention, the

annular pistons are arranged in a sleeve having a cylindrical projectionlocated on the side opposite to the drill steel, the end face of saidprojection, which faces the annular piston, being provided with linkagemembers for cooperation with said piston so as to ensure their combinedmovement in the inner cavity of the fronthead body with the formation ofan additional air chamber'between the end face of the annular piston,which is arranged on the side opposite to the drill steel, and the endface of the cy lindrical pr ojection o f the sleeve, and anotheradditional chamber between the end face of the annular piston, whichfaces the drill steel, and the end face of a sleeve having pawls, saidend face also being provided with linkage members for cooperation withthe annular piston, one of the additional chambers communicating with asource of compressed air so as to cause combined axial movement of theannular pistons towards the opposite additional chamber under airpressure,'the end faces of the pistons, which define the walls of theadditional chambers, being provided with linkage ratchet mechanism or tothe sleeve having the cylindrical projection, said sleeve beingpermanently linked up with the sleeve of the ratchet mechanism and withthe spindle of the drill steel by means of a drive sleeve,

while the annular saiaaraemg'uie 'dfillstel and the ratchet pawls, whichare divided into the pawls for lefthand rotation and the pawls forrighthand rotation, are providedwith linkage members for cooperationtherebetween, switching members also being provided for these pawls,with said switching members and said linkage members causingsimultaneous movement and switching of the left and righthand rotationpawls during the axial movement of the annular pistons, whereby thedirection of rotation of the sleeve of the ratchet mechanism is changedover when it is connected by means of the linkage members to one of theannular pistons where this piston, which rotates in one direction, isblocked, and the other piston is placed in operation, thereby reversingthe rotation of the drive sleeve and the spindle of the drill steel. 7 g7 lt is advantageous that the linkage members providing for cooperationbetween the annular pistons and the cylindrical projection of the sleevesupporting them, as well as the linkage members of the sleeve having thepawls should be fashioned as axial clutch cams which secure engagementof the annular pistons during the transmission of powerfulhigh-frequency torsional impact pulses to the drill steel.

It is also advantageous that the linkage members for cpgperation of theratchet pawls with an annular piston be defined on these pawls in theform of cylindrical rods having annular projections, while the linkagemembers of the annular piston facing the drill steel be defined as anannular groove on the end face of this piston, which faces the drillsteel, with said groove permanently receiving the annular projections ofsaid rods and being adapted to cause, during the movement of the annularpistons, the displacement of the pawls, the length of the rods of thepawls for lefthand and righthand rotation being different by the amountof this dis placement whichres ulfs in simultaneous switching of thepawls for both lefthand and righthand rotation during the reversing ofthe.

rotation and the switching members for the pawls comprise the internalconical chamfers provided in the cylindrical projection of the end faceof the fronthead body facing the drill steel, and in the cylindricalprojection of an intermediate disc mounted in the end face recess of thehousing of the ratchet'rnechanism, said chamfers being extended bycylindrical bores of a diameter which is smaller than the insidediameter of the ratchet wheel (housing), so that during the combinedmovement of the ratchet pawls and the annular pistons towards or awayfrom the drill steel, the working edges of the pawls slide over theconical surface of these chamfers, whereby the pawls both for lefthandand righthand rotation are simultaneously rotated in the sockets of thesleeve of the ratchet mechanism, the pa\ v ls of one rotationaldirectionbeing disengaged from the teeth of the ratch et wheel and beingreceived in the I cylindrical bores which represent the extensions ofthe conical chamfers, while the pawls of the other rotational directionare caused to engage with the teeth of the ratchet wheel, therebyreversing the rotation.

This makes it possible to reverse the rotation of the drive sleeve withthe spindle and the drill steel at any position of the annular pistonsby means of a reliable and simple arrangement of minimum size. 4

It is also advantageous that the drilling machine, be provided withpassages adapted to periodically place the work and idle stroke airchambers in communication with a source of compressed air andatmosphere, said passages comprising an annular inlet passage located onthe outside surface of the annular piston, which is arranged on the sideopposite to the drill steel, and in constant communication with a sourceof compressed air, and an annular exhaust passage located on the outsidesurface of the annular piston, which faces the drill steel, and inconstant communication with the atmosphere, said passages being inconstant communication with longitudinal inlet and exhaust passagesrespectively which are provided in the projections of the annularpistons, with said longitudinal inlet and exhaust passages terminatingon the end faces of the projections of the annular pistons which areconstantly in contact with the end faces of the bottom of theindentations and are communicated with concentric inlet and exhaustpassages, which are locatedton the end faces of these indentations andterminate in the work and idle stroke chambers, the longitudinal inletpassages being periodically communicated with the concentric inletpassages terminating in the identical work and idle stroke chambersduring the reciprocatory angular oscillations of the projections of theannular piston, which at the same time functions as a hammer, while thelongitudinal exhaust passages beir lg i n constant communication withthe concentric exhaust passages, with the concentric inlet and exhaustpassages being defined in such a manner as to communicate the inlet andexhaust passages with the work and idle stroke chambers while the lengthof the concentrical inlet passages terminating in the identical chambersshould be selected proceeding from the condition:

L1/L2 1, which provides for the formation of an air cushion only in thechambers of the work stroke at any rotational direction, wherein L, isangular length of the concentrical inlet passage terminating in the workstroke chamber;

L is angular length of the concentrical inlet passage terminating in theidle stroke chamber. i V, This ensures stable starting and operatingconditions of the impulse rotary frontheadin any intermediate positionof the annular pistons and within either rotational direction.

It is furthermore advantageous that the ratio between the areas of theend faces of each annular piston subjected to the action of compressedair on the side of the additional air chambers and the work and idlestroke chambers fulfil the following condition:

7.5 .45 211W. t M

which ensures a constant pressurei for urging the annular pistonsagainst each other and for reducing compressed air leakage from the workand idle stroke chambers, wherein F, is area of the end face opposite tothe impact projections of one of the annular pistons;

F is area of the end faces of the bottom of the indentations of one ofthe annular pistons on the side of reversible rotation of the drillsteel shown in FIGS. 2 the impact projections in the work or idle stroke'through 9 comprises an air-operated striking rearhead chambers. g V j 6and a rotary impulse fronthead 7. This Provides for constant minimum p 5The air-operated striking rearhead 6 has a body 8 tween the end faces ofthe annular pistons, which are rovided with a V cylindrical boreaccommodafiigan in frictional engagement therebetween, to reducecomair-distribution arrangement (the air-distribution arpressed airleakage, and thereby increase the effirangement and an on/offarrangement are not shown ciency of operation of the impulse rotaryfronthead of i the drawihgs and may be of any appropriate eFlIilEE lhEeEe o ..M .,W, 10 type), and a movable hammer piston 9. The body 8 isAccording to the m e there 13 Provided a P operably coupled with therotary impulse fronthead cussive drilling machine with independentreversible by way of an adapter Sleeve 10.

rotation of a drill steel which has a reversible rotary T reversibleimpulse rotary fromhead 7 has.a body frohtheafi with e e of Constantminimum axial P 11 provided with a cylindrical bore accommodatingautomaheaiiy maintained w e Compressed F? the rotatably mounted axiallymovable annular leakage s eliminated and the efficiency of the machinepistons 12 and 13 fitting into each other, and a Sleeve is increased. Inaddition, the machine is compact and 14 provided with a Cylindricalprojection 15 (on the a e ih ep side opposite to the drill steel 2),with the sleeve being BR F DESCRIPTION OF THE rotatably mounted andaccommodating the annular D DRAWINGS a'igisn' i'zafifi'si" The inventionWlll now be described in detail with The body 11 of the fromhead 7 p i ea cylindril' i t0 the p i embocjimeht thefeof cal tubular member with asleeve 16 press fitted hated the accqmpanymg drawlhgi m which: thereon,so that their outside and inside surfaces re-' FIG- 1 schem y showsdrilling rig e f spectively define passages therebetween. An inletpasdrill deep holes underground using a percussive dl'llllflgl sage 17communicates with a Source of compressed machine according s i visa'piaisaaran'ahaust atsagersraaiaaaeate 2. a longitudinal sequonal l of fwith the atmosphere via radial passages 20. The sive drilling machineaccording to t e invention e toutside Surface of the body 11, the Sleeve16, is also hand rotation) provided with an inlet pipe 21 for lefthandrotatlon FIG. 3 a, b is a cross sectional view taken along the which isadapted to establish communication be L LI I II in F IG 2 the Viewlooking in the direc' tween a source of compressed air via an inlet poit22 ilgnrofgle ZP -T-- and the internal cavity of the body ll, whichdefines i aEi P i. i ii %g a reverse chamber 23 located between the endfaces IV"IV m vlew ookmg m t 6 of the cylindrical projection 15 and theannular piston tion of th e arrows;

FIG. 5 a, b is a cross sectional view taken along the 12 on the'sldaOpposite to the u 2.

---- The annular pistons 12 and 13, which are accommogfi lx f 2 the vlewlookmg m the dlrectlon; idated in the cylindrical bore of the body 11,comprise FIG. 6 is a longitudinal sectional view of the drillingislfieves having annular Impact Projectlons 25 t th hth d t f (FIGS. 3,a, b and 4, a, b). The impact pro ections 24 sjg accor mg 0 e an to and25 of the annular pistons 12 and 13 are received P16 7 a b is a crossfictional View taken alon t e. in the respective indentations formedbetween these line VII vrrm ro' K the View looking in the diicthat theyare f l mmable and the side surfaces of the pro ections 24 and 25 andthe of mews; v... cylindrical surfaces of the body ll and the sleeve 14F 8 b is a cr9cnonal View taken along the! provide air chambers 26 and27 for the work and idle F YIH VHI in G 6 the View looking in the,strokes. The end faces of they bottom of the indentadlrectlon of thearrows tic r s pf th annular pistons are provided with con;

FIG. 9 a, b is a cross sectional view taken along the jrcjehtricpassages namely; inlet 'g m in line IX-IX in FIG. 6 the view looking inthe direc-- the piston 12 and exhaust passages 30 and 31 in the tqiiqith arr ws;..- a MAM aa L piston 13.

DETAILED DESCRIPTION OF THE 7 The outside cylindrical surface of theannular piston INVENTIQN 12 is provided, on the side opposite totheimpact pro- AS Show" in the pg adaRted to drill, jections 24, with anannular inlet passage 32 in con holes underground using the drillingmachine accord-T stant communication with the end faces of these 8 tothe invention Comprises a drilling machine projections via longitudinalpassages 34 provided in which is provided with adrill Steel 2 having athe impact projections 24. The outside cylindrical at the tip insertedin the front part and a feed arrange-' surface of the annular piston 13is provided, on the merit 4 for imposing an axial feed load- The g'.side opposite to the impact projections 25, with an machine 1 and thefeed arrangement 4 are located annular exhaust passage 33 in constantcommunicaa carriage 5 Which tfaiispoi'is these components to tion withthe end faces of thesev projections via face and Performs anmanipulations associated longitudinal passages 35 in the impactprojections 25. With the setting "P of the machine and feed g Theannular inlet passage 32 and the annular exhaust mer t for drill holespassage 33 of the annular pistons 12 and 13 are con- Arrows A, B, C andD indicate the connections of the. nected by means of radial passages 36and 37 .to the drilling machine to the compressed air mains of the inletpassage 17 a source of compressed air and to the mine. 7 Iexhaustpassage 19 atmosphere.

The percussive drilling machine with an independent:

mounted cylindrical sleeve 47. The sleeve 47 is 38 during axial movementof both annular pistons 12,

13 away from the drill steel 2, with the sleeve 14 which is providedwith respective axial cams 41 disposed on the cylindrical projectionthereof. The sleeve 14 is provided with sector earns 42 facing the drillsteel 2 which ensure constant engagement of the s le eve wit h a ratchetmechanism denoted generally 43 (or with a free-wheel mechanism of anyother type).

8 The ratchet mechanism 43 is arranged in the front part of thereversible impulse rotary fronthead 7 (on the side of the drill steel 2)and is accommodated in a housing 44 which is provided with internalratchet teeth 45. The housing 44 is provided with a cylindrical bore onthe side opposite to the drill steelwhich seats,

on an aligning cylindrical projection 46 of the body 11' of the impulserotary fronthead 7. The housing 44 of the ratchet mechanism '43accommodates a rotatably provided with through notches and cylindricalbores which are adapted to accommodate rotatable and axially movablespring loadedithesprings are not s hFWn in the drawings) pawls 48 forlefthand rotation and pawls 49 for righthand rotation. The pawls 48. and49 are provided, on the side opposite to the drill steel 2, withcylindrical rods of different length having annular projections 50 whichare constantly received in the circular groove 40 of the annular piston13 and which are adapted to transmit linear motion to the pawls 48 and49 during the movement of the annular piston 13.

The end faces of the sleeve 47 acc ommodates, on the side opposite tothe drill steel 2, earns 51 adapted to engage the respective cams 39 ofthe annular piston 13, and on the side of the drill steel 2, internalsector cams 52. in addition, on the side of the drill steel 2, thesleeve 47 receives a drive sleeve 53 which engages the sector cams 52 ofthe sleeve 47 with its sector cams 54.

The drive sleeve 53 is accommodated in a cover cap 55 which is fixed tothe housing 44 of the ratchet mechanism 43 and to the body 11 of theimpulse rotary fronthead 7 by means of an intermediate disc 56 and bolts57 with nuts 58.

The intermediate disc 56 is fixed to the housing 44 of the ratchetmechanism 43 by means of a cylindrical projection 59 and is provided, onits outside cylindrical surface, with a pipe 60 for righthand rotationwhich is communicated through a port 61 with a cylindrical bore 62,whose diameter is smaller than the inside diameter of the ratchet wheel.The cylindrical bore 62 is communicated through the notches of thesleeve 47 with a reverse chamber 63 for righthand rotatipn which isprovided between the end faces of the annular piston 13 on the side ofthe drill steel 2 and of the sleeve 47 on the side opposite to the drillsteel 2. The cylindrical projection 59 of the disc 56 is provided with aconical chamfer 64 by means of which the engagement and disengagement ofthe pawls 49 is performed during the reversing of the rotation. Thepawls 49 for righthand ro-: tation, while sliding over the surface ofthe conical chamfer 64, are moved together with the annular pistons l2and 13 away from the drill steel being rotated at the same time in theirsockets, and are received in the cylindrical bore 62 thereby disengagingfrom the ratchet teeth 45 of the housing 44, or in other words. they aredisconnected. The engagement of the pawls 49 takes place in the reverseorder. During the movement of the annular piston 13 away from the drillsteel 2, the pawls 49 leave the cylindrical bore 62 of the disc 56 and,while sliding over the generatrix of the conical chamfer 64, engage theratchet teeth 45 of the housing 44, or in other words, they are engaged.The engagement and disengagement of the pawls 48 for lefthand rotationis performed in the same manner by means of a conical chamfer 65 of thealigning cylindrical projection 46 of the body 11 of the impulse rotaryfronthead 7 and a cylindrical bore 62a during the movement of theannular pistons 12 and 13 away o he dr lst s a V o,

Mounted in the drive sleeve 53 for rotation together therewith is aspindle 66 which is adapted to receive the drill steel 2. The drillingmschmerufiefibism theiairswifigway, the starting position is shown inFIGS. 2, 3a, 4a, 5a, in which the annular piston 13 functions as arotary anvil, and the annular piston 12rests on the air cushion in theWork stroke chamber lefthand rotation.

- When the drilling machine is activated, compressed air (air-and-oilmixture) is fed in the direction indicatedby arrows A, B, C (FIG. 1)from a source of compressed air to.the striking rearhead 6 (A), theinlet pipe 1 8 jBj/a'nd the pipe 21 (C) of the impulse rotary fronthead7 (FIG. 2).

When subject to the pressure of the air admitted into the strikingrearhead 6, the hammer pis ton 9 reciprocates was to deliver, at the endof the work stroke,

blows at the spindle 66 which receives the drill steel 2.

When compressed air is fed through the inlet pipe 21 :of the body ll ofthe impulse rotary fronthead 7, the air enters the reverse chamber 23for lefthand rotation via the inlet port 22. Under the action of airpressure in the reverse chamber 23, the annular pistons 12 and 13 areaxially displaced towards the drill steel 2, while moving over theoutside surface of the sleeve 14. Accordingly, the annular piston 13during the movement in the above-mentioned direction causes the pawls 48and 49't0 move towards the drill steel 2 by means of its circular groove40 and annular projections 50 of the pawls which are received in thisgroove. The pawls 48 for lefthand rotation of the ratchet mechanism 43are caused to disrfice axfilly tbwfils the drill steel 2, leave thecylindrical bore 62a of the body 11, whose diameter is smaller than theinside diameter of the ratchet wheel and. while sliding with theirworking edges over the surface of the conical chamfer 65 of thecylindrical projection 46 of the body 11, are shifted away from thecentral axis of the machine under the action of springs (not shown inthe drawing) and come into engagement with the ratchet teeth 45 of thehousing 44 (ratchet wheel), which means they are engaged.

away from the c eiitral axis ofthe machinefdisengaged from the ratchetteeth 45 and enter the cylindriv cal bore 62 of the disc 56 tafing theirnew position l3 'awa'y from the drifls t e el 2, the axial cams 39 ofthe annular piston 13 engage the respective axial cams 51 of the sleeve47 of the ratchet mechanism 43, which is in constant engagement throughits sector earns 52 (FIG. 5), with the respective sector earns 54 of thedrive sleeve 53 having the spindle 66 of the drill steel receivedtherein, thereby coupling the annular pistons 12 and 13 with the drivesleeve 53 and the spindle 66.

After the annular pistons 12 and l3'have takentheir starting position(FIG. 2), compressed air from a source is fed through the pipe 18 andthe inlet passage 17 of the body 11 into the annular inlet passage 32and into tl 1 e lorgitudinal passages 34 (FIGS. 3 l' l 4) of the annularpiston 12 in communication therewith. Then, the compressed air is fed,via the longitudinal passages 34 of the impact projections 24 of theannular piston l2 into the concentric inlet passages 28 located on theend faces of the indentations of the annular piston 12, which passagesterminate in the work stroke chambers 26. Since the idle stroke chambers27 communicate with the atmosphere via the concentric exhaust passages30 and 31 disposed on the end face of the bottom of the indentations ofthe annular piston 12 provided between the projections of the annularpiston 12, which passages are in communication with the longitudinalexhaust passages 35 in constant communication with the annular exhaustpassage 33 of the annular piston 13 and with the exhaust passages 37, 19and 20 of the body 11 of the rotary fronthead 7, the pressure in theidle stroke chamber 27 is close to the atmospheric one.

The pressure in the work stroke chamber 26 is abruptly increased, andthe impact projections 24 of the annular piston 12 begin to turn towardsthe projections 25 of the annular piston 13 under the action of thepressure difference between the chambers 26 and 27. In so doing, despitethe fact that the compressed air,

which entered the work stroke chambers 27, exerts pressure upon bothside surfaces of the impact projection 24 of the annular piston 12 andof the impact projection 25 of the annular piston 13, only the projections 24 of the piston 12 will start to move, since the piston 13 iscoupled, by means of the axial cams 51 and 39, with the sleeve 47 of theratchet mechanism, whose ratchet pawls 48 are in engagement with theratchet teeth 45 of the housing 44 and block the sleeve 47 of the pawlsand the piston 13 in this position prethe piston 13.

During further movement of the annular piston 12,.

after the longitudinal passages 34 have passed the space Between theconcentric inlet passage; 28 and 29, compressed air enters the idlestroke chambers 27 via the longitudinal passages 34 of the annularpiston 12 and the concentrical inlet passages 29 of the piston 13. Theannular piston 12, while continuing its movement under inertia andcompressing the volume of compressed air in the chamber 27, deliverswith its impact projections 24, ablo w at the. projections 25 6f theannular piston 13. Upon delivering the blow, theannular piston 12 willmove in the opposite direction under the action of the increasedpressure in the chambers 27 and partially as a resplt of the reboundfromthe projections 25 the beginning of the idle stroke.

During the movement of the annular piston 12 away from the point ofimpacting between the projections 24 and 25, the longitudinal inletpassages 34 of the annular piston 12 are disconnected from theconcentric inlet passages 29 of the piston 13, thereby shutting off theadmission of compressed air into the idle stroke chambers27. Duringfurther movement of the annular piston 12 under inertia theidle strokechamber-5273K; comgmu riicated'with th atr'nosph ere ia the concentricexhaust passages 30 and 31 of the piston 12, and longitudinal passages35 and annular passages 33 of the annular piston 13, while the workstroke chambers 26 are communicated with a source of compressed air viathe 30 concentric'inlet passages 2 8 of the piston 13, the longitudinalinlet passages 34 and the annular inlet passage 32 of the piston 12.Since the concentric inlet passages 28 of the annular piston 13, whichterminate in the'work stroke chambers 26, are longer than the con- 35centnc passaQQsQT, which terminate in the idle stroke chambers 27, theadmission of compressed air into the chambers 26 respectivelyanticipates the admission into the chambers 27, whereby the annularpiston 12, which moves under inertia, will begin to be decelerated bythe air cushion formed in the chamber 26 also with anticipation, andwill stop on the air cushion thus formed without reaching theprojections 25 of the piston 13 the end of the idle stroke. At thatinstant, the pressure in the work stroke cham- 5 bers 26 is abruptlyincreased, and the projections 24 of venting them from rotating underthe action of compressed air upon the projections 25. Accordingly, theannular piston 12 performs an angular travel work stYikd-th direction ofmovement afifi'isi'stiffi is indicated by arrows in FIGS. 3a, b and 4a,b.

During its movement, the annular piston disconnects its longitudinalinlet passages 34 from the concentrical inlet passages 28 of the annularpiston 13 so as to shut off the admission of compressed air into'thework exhaust passages 30 and 31 of the moving annular piston 12 and thelongitudinal exhaust passages 35 of the annular piston 12 will movetowards the projections 25 of the piston 13 under the action of thepressure difference between the chambers 26 and '27 (the work strokecycle is repeated). I

Since one of the concentric inlet passages 28, which terminates in oneof the work-stroke chambers 26, and one of the concentric inlet passages29, which terminates in one of the idle stroke chambers 27, are longerthan other concentric inlet passages 28 and 29, the occurrence of a deadcenter during the starting period of the rotary fronthead is eliminatedat any of intermediate angular positions of the projections 24 and 25 ofthe annular pistons 12 and 13.

During the operation of the impulse rotary fronthead 7, the sealing ofthe work and idle stroke chambers 26, 27 and the reduction of airleakage between the end faces of the projections 24, 25 of the annularpistons 12 and 13 in contact therebetween, as well as between these endfaces and the bottom of the indentations prowded between the projectionsare ensured due to the difference between the areas of the annularpiston tw l sbar ybisqts tq hesqn ta t f sq of 9.

pressed air. Thus, the values of forces acting upon the end face areasof the annular piston 12 on'the side opposite to the projections 24,2111area F I, 21d those facing the projections 24, an area F2, are directlyproportional to the values of these areas, and the constant urging ofthe piston 12 against the piston 13 is ensured due to the forcedifference.

Thus, the end faces of the annular pistons 12 and 13, which are infrictional contact therebetween, are rather sufiiciently oiled andcooled with an air-and-oil mixture, which is supplied from an air sourceand distributed via the inlet passages terminating in these end faces,namely via the longitudinal passages 34 and concentric passages 28, 29.

The above-described cycles of operation of the annular pistons arerepeated at high frequency, and the'annular piston 12performsreciprocatory angular oscillations so as to deliver, at the endof every work stroke, a blow with its projections 24 at the projections25 of the piston 13.

Under the action of torsional impact pulses created as a result ofimpacting between the impact projections- 24 and 25 of the annularpistons 12 and 13, the annular piston 13, which performs the functionsof an anvilduring lefthand rotation, is rotated in the direction of theblow and, by means of its axial earns 39, and the axial cams 51 of thesleeve 47 of the ratchet mechanism, rotates the sleeve 47 and the drivesleeve 53 coupled therewith by means of the sector earns 52 and 54, andhence the spindle 66 of the drill steel 2. V

The work and idle stroke cycles are repeated at high frequency, and thesleeve 47 receives periodical rotation under the action of torsionalimpact pulses created as a result of the impacting between the impactprojections 24 of the annular piston 12 and the projections 25 of theannular piston 13, and transmits this rotatio through its own sectorearns 52 and the sector cams I of the drive sleeve 53 to the spindle 66with the drill steel 2.

During the angular motion of the sleeve 47 through some angle a, thespring loaded pawls 48 (FIGS. 5a, b)

accommodated therein are rotated, said pwals, while springly rockingover the ratchet teeth'45 of the housing 44 of the ratchet mechanism 43and being displaced through the same angle a, block the sleeve 47 andthe parts associated therewith at every new variable position, that isthey block the drive sleeve 53 and the spindle 66 with the drill steel2. The pawls 48 prevent these parts from rotating in the oppositedirection under the action of the elastic rebound reactive force of thedrill steel being twisted as a result of its engagement with the rockbeing destructed, 55a mfih tdrsiohal impa ct pulses received by thesleeve 47 are delivered at high. frequency, the sleeve 47 and the partsassociated therewith, that is the drive sleeve 53 with the spindle 66and the drill steel 2, receive substantially continuous lefthandrotation in one direction only.

In order to reverse the rotation, that is, in order to change over forrighthand rotation, the pipe 21 for lefthand rotation is communicatedwith atmosphere, while the pipe 60 (the arrow D) for righthand rotationis communicated with a source of compressed air (FIG. 1). In this case,compressed air is admitted via the inlet port 61 and the cylindricalbore, 62 of the disc 56 and via the through notches of the sleeve 47into the space between the end faces of the sleeve 47 and of the annular piston 13, that is into the reverse chamber 63 for righthandrotation (FIG, 6).

Under the action of pressurejn the reverse chamber 63, the annularpistons 1 3 and 12 are axially displaced away from the drill steel 2moving over the outside surface of the sleeve 14. Therefore, the annularpiston 13, while moving in the above-mentioned direction, causes thepawls 48 and 49 to move away from the drill steel by means of thecircular groove 40 of the piston and of the annular projections 50 ofthe pawls which are re ceived in this groove. The pawls 49 for righthandrotation of the ratehet mechanism 43 are c aused to move aiiallmay fromthe drill steel 2, leave the cylindrical bore 62 of the disc 56 and,while sliding with their working edges over the surface of the conicalchamfer 64 of the cylindrical projection 59 of the disc 56, are shiftedaway from the central axis of the machine under the action of springs(not shown in the drawing), and come intoengagernent with the ratchetteeth 45 of'the Housing 44, that is they are engaged. At the same time,

the pawls 48 for lefthand rotation, which were earlier displaced towardsthe drill steel 2, are caused to move together with the pawls 48 awayfrom the drill steel 2 so that their working edges slide over thesurface of the conical chamfer 65 of the cylindrical projection 46 ofthe body 11, and the pawls are shifted away from the central axis of themachine so as to be disengaged from the ratchet teeth 45 and take theirnew position in the cylindrical bore 62a of the body 11, that is theyare disconnected.

During the movement of the annular pistons 12 and 13 away from the drillsteel 2, the axial earns 38 of the annular piston 12 come intoengagement with the respective axial earns 41 located on the cylindricalprojectio n l a of the sleeve 14, and which sleeve is in constantengagement with the sector earns 52 and 54 of the sleeve 47 of theratchet mechanism and of the drive sleeve 53 with the spindle 66received therein by means of the sector earns 42 of the sleeve 14 (FIG.5), thereby coupling the annular pistons and the drive sleeve with thespindle (FIG. 6).

After the annular pistons 13 and 12 have taken their starting position(FIGS. 6; 7a, b; 8a, b; 9a, b), compressed air is admitted from a sourcethrough the inlet pipe 18 and the inlet passage 17 of the body 11 intothe annular inlet passage 32 and the longitudinal passages 34 of theannular piston 12 in communication therewith. Then the compressed airflows via the longitudinal passages 34 of the annular piston 12 into theconcentrical inlet passages 28, which are located on the end faces ofthe indentations of the annular piston 13, and terminate in the workstroke chambers 26. Since the idle stroke chambers 27 are communicatedwith the atmosphere via the concentrical exhaust passages 30 and 31,which terminate on the end faces of the bottom of the indentations ofthe annular piston 12 provided between the projections 24 of the annularpiston 12 and are in communication with the longitudinal exhaustpassages 35 in constant communication with the annular exhaust passage33 of the annular piston 13 and with the exhaust passages 37, 19 and 20of the body 11 of the rotary fronthead 7, the pressure ,in the idlestroke chambers 27 is near to the atmospheric pressure. p I 7 V Thepressure in the work stroke chamber 26 is abruptly increased, and theimpact projections 25 of the annular piston 13 begin to turn towards theprojections 24 of the annular piston 12 under the action of the pressurediference between the chambers 26 and 27. 1n this case, despite the factthat the compressed air admitted into the idle stroke chambers 27 exertsthe pressure against the both side surfaces of the impact projection 25of the annular piston 13 and of the impact projection 24 of the annularpiston 12, only the projections 25 of the piston 13 will start to move,since the piston 12 is coupling by means of its own axial earns 38 andthaxial cams 41 and 42 of the sleeve 14, with the drive sleeve 53 andwith the sleeve 47 of the ratchet mechanism, whose ratchet pawls 49 arein engagement with the ratchet teeth 45 of the housing 44 and block thesleeve 47, the drive sleeve 53, the sleeve 14 and the piston 12 in thisposition, thereby preventing them from rotating under the action ofpressure of compressed air upon the projections 24. As a result, theannular piston 13 performs an angular travel-work stroke the directionof movement M51565 13 isindicated by arrows in FIGS. 7a, b and 8a, b.

During its movement, the annular piston l3 disconnects its concentricinlet passages 28 from the longimama: 'inle'fpa'ssages 34 'ofthe pistoniraas 165m off the admission of compressed air into the work strokechambers 26, and further movement of the impact projections 25 takesplace due to the energy expansion of the volume of compressed airadmitted into the chambers. At the same time, the work stroke chain:bers 26 are communicated with the annular exhaust passage 33, and hencewith atmosphere, via the concentric exhaust passagest) and 319i" theannular piston 12 and the longitudinalexhaust passages 35 of the movingannular piston 13.

During further movement of the annular piston 13, when the longitudinalpassages 34 of the annular piston 12 have been passed by the spacebetween the concentric inlet passages 28 and 29, compressed air isadmit-' ted into hematite champerswwa the longitudinal passages 34 ofthe annular piston 12 and the concentric inlet passages 29 of theannular piston 13. Then the annularpiston l}, while continuing to moveunder inertia and compressing, in the chamber 27, the volume of the airadmitted therein, delivers a blow with its impact projections 25 at theprojections 24 of the annular piston 12. Upon delivering the blow, underthe action of the increased pressure in the chambers 27, and partiallyas a result of the rebound from the projections 24, the annular piston13 will begin to move in the apposite direction the beginnin g of theidle stroke. During the movement of the annular piston 13 away from thepoint of impacting between the projections 25 $a r1d 24, thelongitudinal inlet passages 34 of the annular P15 9". arsstesanssts i rm t wnsqitt sia st passages 29 of the piston 13, thereby shutting offthe admission of compressed air into the idle stroke chambers 27. Duringfurther movement of the annular piston. 13 under inertia the idle strokechambers 27 are com- 'municated with theatrisphere via the concentric xhaust passages 30 and 31 of the piston l2 and their own longitudinalpassages 35 and circular passage 33, while the work stroke chambers 26are communicated with a source of compressed air via the concentricinlet,

chambers 27, and compressed air is admitted into the chambers 26 with ananticipation with respect to the chambers 27 the annular piston 13moving under inertia will begin to be decelerated by the air cushionfonned in the chamber 26 also with anticipation and will stop withoutreaching the projections 24 of the piston 12 to rest on the air cushionthus formed the end of the idle stroke,

At the same time, the pressure in the work stroke chambers 26 isabruptly increased, and the projections 25 of the annular piston 13 movetowards the projections 24 of the piston 12 under the action of thepressure difference between the work stroke chambers 26 vand the idlestroke chambers 27 the work stroke cycle ispepe ated, A V, V, l We qoqns9 .th i t n t, aassassalii which terminates in one of the -work strokechambers 26, and one Qftheconeentric inlet passages 29, which terriiinat es inone of the idle stroke chambers 27, are made longer thanthe other concentric inlet passages 28 and 29, the formation of a deadcenter during the starting period of the rotary fronthead is eliminated,when the projections 25 and 24 of the annular pistons 13 and 12 are atany one of the intermediate angular positions.

During the operation of the impulse rotary fronthead, '7, the sealing ofthe work and idle stroke chambers 22 and 27 and the reduction. of airleakage between theend faces of the projections 24, 25 of the annularpistons 12 and 13 and the bottom of the indentations providedtherebetween are ensured due to the difference in the areas of thehammer piston 13 subjected to the constant action of compressed air.Thus, the values of forces acting upon the area of the end faces of thepiston 13on the side opposite to the projections 25, an area F and onthe side of the projections 25 an area F are directly proportional tothevalues of these areas,-and the annular piston 13 is permanently urgedagainst the piston 12 due to the force difference.

Therefore, the end faces of the annular pistons 12 and 13, which are infrictional engagement therebetween, are rather sufficiently oiled andcooled with an air-and-oil mixture supplied from a source of compressedair and distributed via the inlet passages located on these end faces,namely, via the longitudinal passages 34 and the concentric passages 28,29.

V The above-described cycles of operation of the annular pistons arerepeated at high frequency, and the annular piston 13' performsreciprocatory angular oscillations so as to deliver, at the end of everywork stroke, a blow with its projections 25 at the projections 24 of theannular piston 12. Under the action of torsional impact pulses createdas a result of impacting between the impact projections 25 and 24 of theannular pistons 13 and 12, the annular piston 12, which functions as ananvil during righthand rotation, is rotated in the direction of theblow. Thus, the annular piston-l2, by means of its axial earns 38 andthe cams 41 of the cylindrical projection 15 of the sleeve 14, cause thelatter to rotate, with the sleeve 14 being coupled by means of itssector cams 42 facing the drill steel 2, with the sector cams 54 of ithedrive sleeve 53 and the cams 52 of the sleeve 47 of thflilchetrnechanism43. V

The work and idle stroke cycles are repeated at high frequency, and thesleeve 47 of the ratchet mechanism receives periodical rotation underthe action of torsional impact pulses created as a result of impactingbetween the impact projccttions 25 of the annular piston 13 and theprojections 24 of the annular piston 12. During the angular motion ofthe sleeve 47 of the ratchet mechanism through some angle a, the springloaded pawls 49 (FIGS. 9a, b) accommodated therein are rotated, saidpawls, while springly rocking over the ratchet teeth 45 of the housing44 of the ratchet mechanism 43 and being displaced through the sameangle a, block the sleeve 47 and the parts associated therewith at everynew variable position, that is they block the drive sleeve 53, and thespindle 66 with the drill steel 2. The pawls 49 prevent these parts fromrotating in the opposite direction under the action of the elasticrebound reactive force of the drill steel being twisted as a result ofits engagement with the rock being distructed, and since the torsionalimpact pulses received. by the sleeve 47 are delivered at highfrequency, the sleeve 47 and the parts associated therewith, that is,the drive sleeve 53 with the spindle 66 and the drill steel 2 receivesubstantially continuous lefthand rotation in one direction only.

What is claimed is:

11 R pa'eus'srvedsriig'aaciirieaavideramr 1 independent rotation of adrill steel located in a front part of the machine, comprising: anair-operated striking rearhead 6 and a rotary impulse fronthead 7; saidair-operated striking rearhead 6 comprising: a body 8 with a cylindricalbore; an air-distribution arrangement and a hammer 9 accommodated in thecylindrical bore of said body 8; said hammer 9 reciprocating under theaction of compressed air so as to deliver, at the end of a work stroke,a blow at the drill steel 2 located in the front part of said drillingmachine 1; said rotary impulse fronthead 7 comprising: a body 11 with acylindrical bore; annular pistons 12 and 13 having impact projections 24and 25 and indentations formed between said projections 24 and 25rotatably accommodated in the cylindrical bore of said body 11, thepistons being coupled by inter-engagement of said projections 24 and 25and the respective indentations thereof; work stroke air chambers 26 andidle stroke air chambers 27 provided between the side surfaces of saidprojections 24 and 25 of the annular pistons 12 and 13 and walls of saidbody 11 of the rotary impulse fronthead 7, said chambers beingperiodically communicated via pa'ssage means with a source of compressedair or atmosphere, and the impact projections 24 and 25 of one of saidannular pistons 12 or 13 performing, under the action of compressed air,high-frequency reciprocatory oscillations with said impact projections24 or 25 at the respective projections 25 or 24 of the other of saidannular pistons 13 or 12 so as to rotate the drill steel 2 viaintermediate partsya sleeve 14 mounted in a cylindrical bore of saidbody 11 of said rotary fronthead 7 having a cylindrical projection 15 onthe side opposite to the drill steel 2, said sleeve supporting saidannular pistons 12 and 13 so that the same can axially move together inthe inner cavity of said rotary fronthead 7; a ratchet mechanism 43located in the front part of said body 11 of the rotary fronthead 7 andcomprising a ratchet wheel integral with a housing 44 of the ratchetmechanism 43, said housing accommodating a sleeve 47 having movablymounted 16 therein spring loaded pawls 48 for lefthand rotation andpawls 49 for righthand rotation which are in engagement with the teeth45 of the ratchet wheel 44, said ratchet mechanism providing forrotation of one of said annular pistons 12 or 13 and the drill steelonly in one direction; an additional reverse air chamber for lefthandrotation located between the end face of the annular piston 12, which isarranged on the side opposite to the drill steel, and the end face ofthe cylindrical projection 15 of said sleeve 14, and another additionalreverse air chamber 63 for righthand rotation located between the endface of the annular piston 13, which faces the drill steel, and the endface of said sleeve 47 of the ratchet mechanism, one of said additionalair chambers 23 or 63 being in communication with a source of compressedair, under the pressure of which a combined axial movement of theannular pistons 12 and 13 away from the opposite additional chamber 63or 23 takes place; coupling members for providing cooperation betweensaid annular pistons 12 and 13 on the one hand, and said sleeve 14having the cylindrical projection 15 and said sleeve 47 of the ratchetmechanism 43 on the other hand, said coupling members being located onthe end face of said cylindrical projection 15 of the sleeve facing theannular pistons 12 and 13, on the end faces of said annular pistons onthe side opposite to the impact projections 24 and 25, and on the endface of said sleeve 47 of the ratchet mechanism facing the annularpistons, said coupling members being so arranged that by means of thesecoupling members 38, 41, the annular piston 12, which is arranged on theside opposite to the drill steel 2, can be coupled during the combinedmovement of the annular pistons 12 and 13 away from the drill steel 2,with the sleeve 14 via said annular projection 15, which sleeve isconstantly connected to the ratchet mechanism 43 which transmitsrighthand rotation to the drill steel via intermediate parts at thisposition of the annular pistons 12 and 13, while the annular piston 13facing the drill steel can be coupled, during the combined movement ofthe annular pistons 12 and 13 towards the drill steel, with said sleeve47 of the ratchet mechanism which transmits lefthand rotation to thedrill steel via intermediate parts at this new position of the annularpistons 12 and 13; switching members of the ratchet pawls for righthandand lefthand rotation of the drill steel, said switching members and Isaid coupling members being adapted to perform simultaneous movement andswitching of both said ratchet pawls 48 for lefthand rotation and theratchet pawls 49 for righthand rotation during the combined axialmovement of the annular pistons 12 and 13 towards and away from thedrill steel, whereby the rotational direction of said sleeve 47 of theratchet mechanism 43 is changed over when it is coupled, by means of thecoupling members, with one of said annular pistons 12 or 13, whichrotated in one direction, where this piston 12 or 13 is blocked, and theother piston 13 or 12 is placed in operation, thereby reversing therotation of the drill steel.

2. The drilling machine according to claim 1, wherein the linkagemembers between the annular pistons on the one hand, and the cylindricalprojection of the sleeve supporting the pistons, and the sleeve havingthe pawls of the ratchet mechanism on 3. The drilling machine accordingto claim 1,

wherein the coupling members for cooperation between the ratchet pawls48 and 49 and the annular piston 13 are provided on said pawls in theform of cylindrical rods having annular projections 50 and on theannular piston 13 in the form of an annular groove 40 located on the endface of said piston facing the drill steel, said rods being permanentlyreceived with their annular projections 50 in said groove, and said rodscausing the pawls 48 and 49 to more during the movement of the annularpistons 12 and 13, the length of the rods of the pawls 48 and 49 forlefthand rotation and for righthand rotation being different by theamount of this movement, whereby simultaneous switching of both thepawls 48 for lefthand rotation and the pawls 49 for righthand rotationis achieved during the reversing of the rotation, while the switchingmembers for the pawls 48 and 49 comprise inner conical chamfers 65 and64 in a cylindrical projection 46 of the end face of the body 11 of therotary fronthead 7 facing the drill steel2 and in a cylindrical projection 59 of an intermediate disc 56 mounted in an end face recess ofthe housing 44 of the ratchet mechanism 43 also facing the drill steel2, the conical chamfers being extended by cylindrical bores 62a and 62,whose diameter is smaller than the inside diameter of the ratchet wheel44, and during the combined movement of the ratchet pawls 48 and 49 andthe annular pistons 12 and 13 towards or away from the drill steel 2,the working edges of the ratchet pawls 48 and 49 slide over the conicalsurface of said chamfers 65 and 64, whereby both the pawls 48 forlefthand rotation and the pawls 49 for righthand rotation aresimultaneously rotated in the sockets of the sleeve 47 of the ratchetmechanism 43, the pawls 48 or 49 for one direction of rotation beingdisengaged from the teeth 45 of the ratchet wheel 44 and received in thecylindrical bores 62 or 62a, which represent the extensions of the'conical chamfers 64 and 65, while the pawls 49 or 48 for a new directionof rotation coming into engagement with the teeth 45 of the ratchetwheel 44, thereby reversing the rotation.

4. The drilling machine according to claim 1, cornoutside surface of theannular piston 12, which is arranged on the side opposite to the drillsteel 2, and in constant communication with a source of compressed air,and an annular exhaust passage 33 located on the outside surface of theannular piston 13 facing the drill steel 2 and in constant communicationwith atmosphere, said passages being in communication with longitudinalinlet passages 34 and longitudinal exhaust passages 35 respectivelywhich are provided in the projections 24, 25 of the annular pistons 12and 13, characterized in that the longitudinal inlet, passages 34 andexhaust passages 35 terminate on the end faces of the projections 24 and25 of the annular pistons 12 and 13, which are constantly in contactwith the end faces of the bottom of the indentations, and are incommunication with concentric inlet passages 28, 29 and exhaust passages30, 31, which are located on the end face of said indentations andterminate in the work stroke chambers 26 and idle stroke chambers 27,the longitudinal inlet passages 34 being periodically communicated withthe concentric inlet passages 28 or 29 terminating in the identicalworkstroke and idle stroke chambers 26 and 27 during the reciprocatoryangular oscillations of the projections 24 and 25 of the annular piston12 or 13 which at the same time functions as a hammer, while thelongitudinal exhaust passages 35 are in constant communication with theconcentric exhaust'passages 30 and 31, the concentric inlet passages 28and 29 and the concentric exhaust pas'sage 30, 31establishingcommunication between the longitudinal inlet passages 34 andthe longitudinal exhaust passages 35 on the one hand, and the workstroke and idle stroke chambers 26 and 27 on the other hand,

while the concentric inlet passages 28 and 29 which terminate in theidentical chambers 26 and 27 are of such a length as to fulfil thefollowing conditions:

which 5miae 'rafgng braaaaa artist cushion pistons against each otherand for a reduction of comk

1. A percussive drilling machine provided with independent rotation of a drill steel located in a front part of the machine, comprising: an air-operated striking rearhead (6) and a rotary impulse fronthead (7); said air-operated striking rearhead (6) comprising: a body (8) with a cylindrical bore; an airdistribution arrangement and a hammer (9) accommodated in the cylindrical bore of said body (8); said hammer (9) reciprocating under the action of compressed air so as to deliver, at the end of a work stroke, a blow at the drill steel (2) located in the front part of said drilling machine (1); said rotary impulse fronthead (7) comprising: a body (11) with a cylindrical bore; annular pistons (12 and 13) having impact projections (24 and 25) and indentations formed between said projections (24 and 25) rotatably accomodated in the cylindrical bore of said body (11), the pistons being cOupled by inter-engagement of said projections (24 and 25) and the respective indentations thereof; work stroke air chambers (26) and idle stroke air chambers (27) provided between the side surfaces of said projections (24 and 25) of the annular pistons (12 and 13) and walls of said body (11) of the rotary impulse fronthead (7), said chambers being periodically communicated via passage means with a source of compressed air or atmosphere, and the impact projections (24 and 25) of one of said annular pistons (12 or 13) performing, under the action of compressed air, high-frequency reciprocatory oscillations with said impact projections (24 or 25) at the respective projections (25 or 24) of the other of said annular pistons (13 or 12) so as to rotate the drill steel (2) via intermediate parts; a sleeve (14) mounted in a cylindrical bore of said body (11) of said rotary fronthead (7) having a cylindrical projection (15) on the side opposite to the drill steel (2), said sleeve supporting said annular pistons (12 and 13) so that the same can axially move together in the inner cavity of said rotary fronthead (7); a ratchet mechanism 43 located in the front part of said body (11) of the rotary fronthead (7) and comprising a ratchet wheel integral with a housing (44) of the ratchet mechanism (43), said housing accomodating a sleeve (47) having movably mounted therein spring loaded pawls (48) for lefthand rotation and pawls (49) for righthand rotation which are in engagement with the teeth (45) of the ratchet wheel (44), said ratchet mechanism providing for rotation of one of said annular pistons (12 or 13) and the drill steel only in one direction; an additional reverse air chamber for lefthand rotation located between the end face of the annular piston (12), which is arranged on the side opposite to the drill steel, and the end face of the cylindrical projection (15) of said sleeve, (14), and another additional reverse air chamber (63) for righthand rotation located between the end face of the annular piston (13), which faces the drill steel, and the end face of said sleeve (47) of the ratchet mechanism, one of said additional air chambers (23 or 63) being in communication with a source of compressed air, under the pressure of which a combined axial movement of the annular pistons (12 and 13) away from the opposite additional chamber (63 or 23) takes place; coupling members for providing cooperation between said annular pistons (12 and 13) on the one hand, and said sleeve (14) having the cylindrical projection (15) and said sleeve (47) of the ratchet mechanism (43) on the other hand, said coupling members being located on the end face of said cylindrical projection (15) of the sleeve facing the annular pistons, (12 and 13), on the end faces of said annular pistons on the side opposite to the impact projections (24 and 25), and on the end face of said sleeve (47) of the ratchet mechanism facing the annular pistons, said coupling members being so arranged that by means of these coupling members (38,41), the annular piston (12), which is arranged on the side opposite to the drill steel (2), can be coupled, during the combined movement of the annular pistons (12 and 13) away from the drill steel (2), with the sleeve (14) via said annular projection (15), which sleeve is constantly connected to the ratchet mechanism (43) which transmits righthand rotation to the drill steel via intermediate parts at this position of the annular pistons (12 and 13), while the annular piston (13) facing the drill steel can be coupled, during the combined movement of the annular pistons (12 and 13) towards the drill steel, with said sleeve (47) of the ratchet mechanism which transmits lefthand rotation to the drill steel via intermediate parts at this new position of the annular pistons (12 and 13); switching members of the ratchet pawls for righthand and lefthand rotation of the drill steel, said switching members and said coupling members being adapted to perform simultaneous movement and switching of botH said ratchet pawls (48) for lefthand rotation and the ratchet pawls (49) for righthand rotation during the combined axial movement of the annular pistons (12 and 13) towards and away from the drill steel, whereby the rotational direction of said sleeve (47) of the ratchet mechanism (43) is changed over when it is coupled, by means of the coupling members, with one of said annular pistons, (12 or 13), which rotated in one direction, where this piston (12 or 13) is blocked, and the other piston (13 or 12) is placed in operation, thereby reversing the rotation of the drill steel.
 2. The drilling machine according to claim 1, wherein the coupling members between the annular pistons on the one hand, and the cylindrical projection of the sleeve supporting the pistons, and the sleeve having the pawls of the ratchet mechanism on the other hand, comprise axial clutch cams respectively.
 3. A drilling machine according to claim 1, wherein the coupling members for cooperation between the ratchet pawls (48 and 49) and the annular piston (13) are provided on said pawls in the form of cylindrical rods having annular projections (50) and on the annular piston (13) in the form of an annular groove 40 located on the end face of said piston facing the drill steel, said rods being permanently received with their annular projections (50) in said groove, and said rods causing the pawls (49 and 49) to move during the movement of the annular pistons (12 and 13), the length of the rods of the pawls (48 and 49) for lefthand rotation and for righthand rotation being different by the amount of this movement, whereby simultaneous switching of both the pawls (48) for lefthand rotation and the pawls (49) for righthand rotation is achieved during the reversing of the rotation, while the switching members for the pawls (48 and 49) comprise inner conical chamfers (65 and 64) in a cylindrical projection (46) of the end face of the body (11) of the rotary fronthead (7) facing the drill steel (2) and in a cylindrical projection (59) of an intermediate disc (56) mounted in an end face recess of the housing (44) of the ratchet mechanism (43) also facing the drill steel (2), the conical chamfers being extended by cylindrical bores (62 and 62), whose diameter is smaller than the inside diameter of the ratchet wheel (44), and during the combined movement of the ratchet pawls (48 and 49) and the annular pistons (12 and 13) towards or away from the drill steel (2), the working edges of the ratchet pawls (48 and 49) slide over the conical surface of said chamfers (65 and 64), whereby both the pawls (48) for lefthand rotation and the pawls (49) for righthand rotation are simultaneously rotated in the sockets of the sleeve (47) of the ratchet mechanism (43), the pawls (48 or 49) for one direction of rotation being disengaged from the teeth (45) of the ratchet wheel (44) and received in the cylindrical bores (62 or 62a), which represent the extensions of the conical chamfers (64 and 65), while the pawls (49 or 48) for a new direction of rotation coming into engagement with the teeth (45) of the ratchet wheel (44), thereby reversing the rotation.
 4. The drilling machine according to claim 1, comprising passage means which are adapted to periodically communicate the work stroke chambers (26)and the idle stroke chambers (27) with a source of compressed air and atmosphere, said passage means comprising an annular inlet passage (32) located on the outside surface of the annular piston (12), which is arranged on the side opposite to the drill steel (2), and in constant communication with a source of compressed air, and an annular exhaust passage (33) located on the outside surface of the annular piston (13) facing the drill steel (2) and in constant communication with atmosphere, said passages being in communication with longitudinal inlet passages (34) and longitudinal exhaust passages (35) respectively which are provided in the projections (24, 25) of the annular pistons (12 and 13), characterized in that the longiTudinal inlet, passages (34) and exhaust passages (35) terminate on the end faces of the projections (24 and 25) of the annular pistons (12 and 13), which are constantly in contact with the end faces of the bottom of the indentations, and are in communication with concentric inlet passages (29, and 29) and exhaust passages (30, 31), which are located on the end face of said indentations and terminate in the work stroke chambers (26) and idle stroke chambers (27), the longitudinal inlet passages (34) being periodically communicated with the concentric inlet passages (28 or 29) terminating in the identical work stroke and idle stroke chambers (26 and 27) during the reciprocatory angular oscillations of the projections (24 and 25) of the annular piston (12 or 13) which at the same time functions as a hammer, while the longitudinal exhaust passages (35) are in constant communication with the concentric exhaust passages (30 and 31), the concentric inlet passages (28 and 29) and the concentric exhaust passage (30, 31) establishing communication between the longitudinal inlet passages 34 and the longitudinal exhaust passages (35) on the one hand, and the work stroke and idle stroke chambers (26 and 27) on the other hand, while the concentric inlet passages (28 and 29) which terminate in the identical chambers (26 and 27) are of such a length as to fulfil the following conditions L1/L2 > 1, which provides for the formation of an air cushion only in the work stroke chambers (26) at any rotational direction, wherein L1 is length (angular) of the concentric inlet passage (28) which terminates in the work stroke chambers; L2 is length (angular) of the concentric inlet passage (29) which terminates in the idle stroke chamber (27).
 5. The drilling machine according to claim 1, wherein the ratio between the areas of the end faces of each of the annular pistons subjected to the action of compressed air on the side of the additional air chambers and on the side of the work or idle stroke chambers fulfils the following condition: F1/F2 > 1, which provides for a permanent urging of the annular pistons against each other and for a reduction of compressed air leakage from the work stroke chambers and idle stroke chambers, wherein F1 is area of the end face of one of the annular pistons on the side opposite to the impact projections; F2 is area of the end faces of the bottom of the indentations of one of the annular pistons in the work or idle stroke chamber on the side of the impact projections. 